Solenoids for use in engine starting mechanisms



April 28, 1970 E. J. BIRD I 3,509,505

SOLENOIDS FOR USE IN ENGINE STARTING MECHANISMS Filed Aug. 24,1967

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United States Patent 3,509,506 SOLENOIDS FOR USE IN ENGINE STARTING MECHANISMS Edmund John Bird, Great Barr, Birmingham, England,

assignor to Joseph Lucas (Industries) Limited, Birmingham, England Filed Aug. 24, 1967, Ser. No. 662,924 Claims priority, application Great Britain, Sept. 9, 1966, 40,311/ 66 Int. Cl. H01f 7/13 US. Cl. 335-274 1 Claim ABSTRACT OF THE DISCLOSURE A solenoid, particularly for use in engine starting mechanisms, includes a body, a plunger slidable within the body, a spring acting between the body and plunger for urging the plunger to a rest position, and a winding for moving the plunger against the action of the spring, the plunger including a main body and an axially extending plate secured to one end of the body, said plate.incorporating at least two radially extending fingers defining a bearing surface for the spring.

This invention relates to solenoids of the kind including a body, a plunger slidable within the body, a spring acting between the body and the plunger for urging the plunger to a rest position, and a winding for moving the plunger against the action of the spring.

According to the invention, in a solenoid of the kind specified, the plunger includes a main part, and an axially extending plate secured to one end of the main part, said plate incorporating at least two radially extending fingers defining a bearing surface for said spring.

The arrangement specified in the preceding paragraph enables a far shorter main part to be employed than in a conventional solenoid. Thus, in a typical solenoid, the plunger is cylindrical with a flange at one end against which the spring acts. However, the portion of the plunger adjacent to the flange is magnetically unnecessary in many instances, and it has been found that a suitable bearing surface for the spring can be provided by fingerson a plate secured to the main part, thereby permitting a considerable shortening of the main part, and consequent saving in material and cost.

In the accompanying drawings FIGURE 1 is a partsectional side view of a solenoid in accordance with one example of the invention and FIGURE 2 is a side view showing the relationship of the solenoid with the engine starting mechanism.

Referring to the drawing, the solenoid includes a multipart body 11 carrying the windings 12 of the solenoid, and a plunger 13 axially 'slidable within the body. The body also carries a contact assembly indicated generally by the reference numeral 14. This assembly includes an axially movable spindle 21, one end of which is slidable in and extends from a passage in the pole 20 of the solenoid, and the other end of which is slidable in a passage in an insulating end cap 29 secured to the body 11. On the spindle 21 are located a pair of cup-shaped parts 22, 2.3. A spring 24 acts between the part 22 and an insulating bush 25, which engages a contact plate 26 bearing against an insulating washer 27, so that the spring 24 urges the entire assembly 25, 26, 27 against the part 23. A further spring 28 acts between the part 23 and the end 3,509,506 Patented Apr. 28, 1970 ice cap 29, which carries a pair of diametrically opposite contacts 32 which are bridged by the plate 26 when the spindle is moved axially by the plunger 13 upon energisation of the solenoid.

At the end opposite the assembly 14, the solenoid plunger has secured thereto a plate which is formed as a metal pressing and includes a pair of outer arms 15, 16 extending from a transverse flange 17 brazed to the p1unger 13. The arms 15, 16 terminate at their ends in notched fingers which serve as a bearing surface for a spring 19, the other end of which acts on the main part of the solenoid to urge the plunger to its normal position.

The plate further includes a central arm 18 having therein a rectangular hole 18a. Engaged in the hole 18a is one arm of a plate 31 having three equi-angularly spaced arms serving as a bearing surface for a spring 30, the other end of which acts on the plunger to urge the plate 31 towards the left hand end of the hole 18a.

In use, one end of a lever 41 is trapped between the plate 31 and the end of the hole 180, the lever being mounted for angular movement with its opposite end secured through a lost motion connection 42 to a pinion 43 which is axially movable into engagement with a tooth wheel on an engine to be started. When it is desired to start the engine, the start switch is actuated, and serves to energise the solenoid, so that the plunger 13 is moved to the right against the action of the spring 19. This axial movement of the plunger serves to move the lever 41 angularly, so that the pinion 43 is moved into engagement with the toothed wheel 44. At the same time as the pinion is moved into engagement with the toothed wheel, the plunger 13 moves the spindle 21 to a position to bridge contacts 32 by way'of plate 26, so operating the starter motor, which then drives the pinion to start the engine. In the event of tooth-to-tooth engagement between the pinion and toothed wheel, the lever 41 continues to move as permited by its lost motion connection 42 with the pinion 43, so that the contacts 32 are closed and the starter motor indexes the pinion so that it engages the toothed wheel.

When the engine has fired, the pinion 43 is thrown out of engagement with the toothed wheel 44, and when the starter switch is released the parts of the solenoid are returned by the various springs to the position shown in the drawing. However, if the starter switch is released before the engine fires, the pinion 43 will still be in engagement with the toothed wheel, so that the lever 41 cannot move, and the plate 31 is efiectively fixed. In these circumstances, the plunger 13 will be moved against the action of the spring 30 to break the contacts, so that the motor is de-energised, whereupon the pinion is disengaged by the spring 19.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A solenoid for use in engine starting mechanism of the kind in which energisation of the solenoid serves through a lever to engage a pinion with a toothed wheel on the engine to be started, said solenoid comprising a body, a plunger, means mounting said plunger for sliding movement in said body, said plunger including a main part, and an axially extending plate secured to one end of said main part, said plate incorporating at least two radially extending fingers, a first spring acting at one end on said fingers and bearing at its other end on said body, a winding for moving the plunger against the action of the first spring, contacts which are closed by 3 movement of said plunger against the action of the first spring, the contacts when closed serving to complete a circuit to said starter motor, resilient means urging said contacts to an open position, an arm formed integrally with said plate and extending axially relative to said plunger, said arm having therein an elongated hole, a member slidable in said hole a second spring acting between said member and the plunger and urging said member to a position in which said lever is trapped between said member and the end of said elongated hole, said elongated hole permitting lost motion of said plunger relative to said member against the action of the second spring, said lost motion permitting the solenoid plunger to be returned to its rest position to open said contact I while said member is held stationary as a result of the toothed Wheel and pinion being engaged.

References Cited UNITED STATES PATENTS 2,783,340 2/1957 Davies et al 335260 XR 3,177,368 4/1965 Seilly 29038 FOREIGN PATENTS 1,151,983 7/1963 Germany.

GEORGE HARRIS, Primary Examiner U.S. C1. X.R. 

